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Different Possibilities (different + possibility)
Selected AbstractsEnantioseparation of amino acids, ,-hydroxy acids, and dipeptides by ligand-exchange CEC using silica-based chiral stationary phasesELECTROPHORESIS, Issue 16 2009Elfriede Pittler Abstract This work deals with the application of silica-based ligand-exchange chiral stationary phases (CSPs) for the enantioseparation of underivatised amino acids, ,-hydroxy acids, and dipeptides with packed CEC. Two different possibilities of preparing silica-based CSPs are presented. One phase contains L -4-hydroxyproline chemically bonded via a spacer to 3,,m silica material. The other approach makes use of N -decyl- L -4-hydroxyproline dynamically coated on a reversed-phase packed capillary. Dynamical coating of reversed-phase material represents a simple alternative to prepare CSP. A comparison of the chemically bonded phase with the dynamically coated CSP by means of resolution of complex-forming analytes is presented. The chemically bonded phase was found to be superior to the dynamically coated phase in terms of resolution of amino acids and dipeptides. However, the dynamically coated CSP was found to be especially suitable for the separation of ,-hydroxy acids. Both techniques are applicable for enantiomer purity tests. [source] Helicobacter pylori"Rescue" Therapy After Failure of Two Eradication TreatmentsHELICOBACTER, Issue 5 2005Javier P. Gisbert ABSTRACT Nowadays, apart from having to know well first-line eradication regimens, we must also be prepared to face Helicobacter pylori treatment failures. Therefore, in designing a treatment strategy we should not focus on the results of primary therapy alone, but also on the final , overall , eradication rate. After failure of a combination of proton pump inhibitor (PPI), amoxicillin, and clarithromycin, the use of empirical quadruple therapy (PPI,bismuth,tetracycline,metronidazole), has been generally used as the optimal second-line therapy. Even after two consecutive failures, several studies have demonstrated that H. pylori eradication can finally be achieved in almost all patients if several "rescue" therapies are consecutively given. It seems that performing culture even after a second eradication failure may not be necessary, as it is possible to construct an overall strategy to maximize H. pylori eradication, based on the different possibilities of empirical treatment (when antibiotic susceptibilities are unknown). Thus, if one does not want to perform culture before the administration of the third treatment after failure of the first two, different empirical treatments exist, including regimens based on: 1, amoxicillin (amoxicillin,PPI at high doses); 2, amoxicillin plus tetracycline (PPI,bismuth,tetracycline,amoxicillin, or ranitidine,bismuth,citrate,tetracyline,amoxicillin); 3, rifabutin (rifabutin,amoxicillin,PPI); 4, levofloxacin (levofloxacin,amoxicillin,PPI); and 5, furazolidone (furazolidone,bismuth,tetracycline,PPI). [source] Tuning the Amphiphilicity of Building Blocks: Controlled Self-Assembly and Disassembly for Functional Supramolecular Materials,ADVANCED MATERIALS, Issue 28 2009Yapei Wang Abstract Amphiphilicity is one of the molecular bases for self-assembly. By tuning the amphiphilicity of building blocks, controllable self-assembly can be realized. This article reviews different routes for tuning amphiphilicity and discusses different possibilities for self-assembly and disassembly in a controlled manner. In general, this includes irreversible and reversible routes. The irreversible routes concern irreversible reactions taking place on the building blocks and changing their molecular amphiphilicity. The building blocks are then able to self-assemble to form different supramolecular structures, but cannot remain stable upon loss of amphiphilicity. Compared to the irreversible routes, the reversible routes are more attractive due to the good control over the assembly and disassembly of the supramolecular structure formed via tuning of the amphiphilicity. These routes involve reversible chemical reactions and supramolecular approaches, and different external stimuli can be used to trigger reversible changes of amphiphilicity, including light, redox, pH, and enzymes. It is anticipated that this line of research can lead to the fabrication of new functional supramolecular assemblies and materials. [source] Piecewise divergence-free discontinuous Galerkin methods for Stokes flowINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 5 2008Peter Hansbo Abstract In this paper, we consider different possibilities of using divergence-free discontinuous Galerkin methods for the Stokes problem in order to eliminate the pressure from the discrete problem. We focus on three different approaches: one based on a C0 approximation of the stream function in two dimensions (the vector potential in three dimensions), one based on the non-conforming Morley element (which corresponds to a divergence-free non-conforming Crouzeix,Raviart approximation of the velocities), and one fully discontinuous Galerkin method with a stabilization of the pressure that allows the edgewise elimination of the pressure variable before solving the discrete system. We limit the analysis in the stream function case to two spatial dimensions, while the analysis of the fully discontinuous approach is valid also in three dimensions. Copyright © 2006 John Wiley & Sons, Ltd. [source] Water in Stereoselective Organocatalytic ReactionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009Michelangelo Gruttadauria Abstract In this review, recent advances in asymmetric organocatalytic reactions carried out with variable amounts of water, from substoichiometric to a large excess (reaction medium), are discussed. We also summarize several proposed mechanisms for the different possibilities of the action of water both in the increased activity of the catalyst and in the asymmetric induction. Finally, the application of this catalytic methodology to the enantioselective synthesis of valuable compounds through enamine or iminium catalysis is presented. [source] Regulation of transgene expressionACTA OPHTHALMOLOGICA, Issue 2009P KOCH Purpose Regulation of the transgene expression in the targeted cells is of course of major importance when using gene therapy. Actually, we have a huge range of possibilities to regulate gene expression. Methods There are two main classes of promoters: constitutive and inducible promoters. Amongst constitutive promoters, we have two sub-forms: non-tissue and tissue specific promoters. The lasts allows us to better target the tissue or cells in which we want to express our gene of interest. On the other hand, inducible promoters have been widely developed recently and allow us to obtain a regulated expression, depending on different factors. Very recently, disease specific inducible promoters emerged for a more precise regulation. Results We will together examine more precisely the different possibilities offered by gene regulation in Gene Therapy. Thereafter, we will more specifically describe usable promoters in ocular inflammation. Finally we will examine the effects of some inflammatory, disease specific, promoters. Conclusion Regulation of transgene expression is one of the fundaments of efficient gene transfer. Recent developments actually allow us to play within the targeted cell(s) to obtain an expression in specific conditions. [source] | ||||||||||